Remember that the formula to calculate the average rate of change is equal to
[tex]\frac{f(b)-f(a)}{b-a}[/tex]
we have that
a=2010
b=2015
f(a)=f(2010)=36.5
f(b)=f(2015)=39.1
substitute
[tex]\frac{39.1-36.5}{2015-2010}=0.52[/tex]
therefore
the answer is 0.52 million per year
